how to vectorize this for loops?

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Siddhesh Karbhari 2018-1-10

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/376516-how-to-vectorize-this-for-loops

编辑： per isakson 2018-1-13

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Siddhesh Karbhari 2018-1-10

编辑：per isakson 2018-1-13

在 MATLAB Online 中打开

clc,
octave=3;
lavel=3;
sigma0=sqrt(2);
for i=1:octave
    temp_D=D{i};
    for j=1:level
        scale=sigma0*sqrt(2)^(1/level)^((i-1)*level+j)
        p=(level)*(i-1);
        figure(1);
        subplot(octave,level,p+j);
        f=fspecial('gaussian',[1,floor(6*scale)],scale);
        L1=temp_img;
        if(i==1&&j==1)
            L2=conv2(temp_img,f,'same');
            L2=conv2(L2,f','same');
            temp_D(:,:,j)=L2-L1;
            imshow(uint8(255 * mat2gray(temp_D(:,:,j))));
            L1=L2;
        else
            L2=conv2(temp_img,f,'same');
            L2=conv2(L2,f','same');
            temp_D(:,:,j)=L2-L1;
            L1=L2;
            if(j==level)
                temp_img=L1(2:end-1,2:end-1);
            end
            imshow(uint8(255 * mat2gray(temp_D(:,:,j))));
        end
    end
    D{i}=temp_D;
    temp_img=temp_img(1:2:end,1:2:end);
    temp_img=padarray(temp_img,[1,1],'both','replicate');
end

Jan 2018-1-10

在 MATLAB Online 中打开

By the way:

% Simpler:
% sigma0 * sqrt(2) ^ (1/level) ^ ((i-1)*level+j)
  sigma0 * sqrt(2) ^ (i - 1 + j / level)

With a proper indentation the code looks cleaner: Ctrl-A Ctrl-I

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Answer 1

Jan 2018-1-10

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/376516-how-to-vectorize-this-for-loops#answer_299514

Neither the inner nor the outer loop can be vectorized. The two imshow commands are impossible to vectorize. Do you really need them? Do you want a vectorization to increase the speed? Then start with using the profiler to find the most time consuming part of the code.